Increasing gravimetric capacity in batteries

Abstract

A sodium-ion battery includes an electrode having a crystalline active material represented by formula units that intercalate and/or deintercalate more than two charge carriers during operation of the battery. In some instances, the active material that experiences a volume change of less than 6.0%, 4.0%, or even 2.0% when the active material intercalates more than two charge carriers during operation of the battery.

The invention claimed is: 
     
       1. A sodium-ion battery, comprising:
 an electrode having a crystalline active material with formula units Na x V 2 -z Q z (PO 4 ) 2 F 3−2y O 2y  that intercalates and/or deintercalates an average of more than two charge carriers during operation of the battery, wherein Q does not represent vanadium and is one or more components selected from a group consisting of redox-active metal cations and metalloid cations; 
 3≤x≤4; 
 0≤y≤1; 
 0≤z<2; 
 when z is 0, x is >3; and 
 when y is 0, z is >0. 
 
     
     
       2. The battery of  claim 1 , wherein z is 0 and x is >3. 
     
     
       3. The battery of  claim 1 , wherein the active material is represented by Na 4 V 2 (PO 4 ) 2 FO 2 . 
     
     
       4. The battery of  claim 1 , wherein the active material represented by Na x V 2−z Q z (PO 4 ) 2 F 3−2y O 2y  is present in the electrode before the initial charge of the battery. 
     
     
       5. The battery of  claim 1 , wherein z is >0. 
     
     
       6. The battery of  claim 4 , wherein x is >3. 
     
     
       7. The battery of  claim 1 , wherein the active material is represented by Na x V 2−z Al z (PO 4 ) 2 F 3  where 0≤z<2 and 3≤x≤4. 
     
     
       8. The battery of  claim 1 , wherein the active material is represented by Na 3 V 2−z Al z (PO 4 ) 2 F 3  with 0≤z<2. 
     
     
       9. The battery of  claim 1 , wherein the electrode is a positive electrode or a cathode. 
     
     
       10. The battery of  claim 1 , wherein the active material multiple octahedral structures that share a common atom,
 the formula units each includes multiple screening ions, 
 each of the screening ions is included in one of the octahedral structures at a vertex opposite from the common atom that is included in the same octahedral structure, 
 an axis extends between the screening ions in the same formula unit, 
 more than three sodium charge carriers are located between the octahedral structures and around the axis. 
 
     
     
       11. The battery of  claim 10 , wherein at least one of the screening ions is an oxygen anion (O 2− ). 
     
     
       12. The battery of  claim 10 , wherein each of the screening ions is an oxygen anion. 
     
     
       13. The battery of  claim 12 , wherein at least one of the octahedral structures has a central atom that is not vanadium and is selected from a group consisting of metals and metalloid cations. 
     
     
       14. The battery of  claim 10 , wherein the octahedral structures share only one common atom. 
     
     
       15. The battery of  claim 1 , wherein the active material experiences a volume change of less than 6% when intercalating more than two charge carriers. 
     
     
       16. The battery of  claim 15 , wherein the active material experiences a volume change of less than 4% when intercalating three charge carriers. 
     
     
       17. A sodium ion battery, comprising: an electrode having an active material represented by Na x V 2−z Q z (PO 4 ) 2 F 3−2y O 2y , wherein
 Q is selected from Al, Ga, In, Sn, and Bi; 
 3≤x≤4; 
 0≤y≤1; 
 0≤z<2; 
 when z is 0, x is >3; and 
 when y is 0, z is >0. 
 
     
     
       18. A system, comprising:
 a sodium-ion battery comprising an electrode having an active material represented by Na x V 2−z Al z (PO 4 ) 2 F 3 , wherein 
 0≤z<2; 
 3≤x≤4; and 
 electronics for controlling the discharge of the battery such that the battery is discharged to a voltage less than 2.0 V or less than 1.8 V. 
 
     
     
       19. The sodium-ion battery of  claim 1 , wherein the electrode has an energy density greater than 500 Wh/kg.